Method of making finned tubes



Nov. 3, 1931. H. -w. BUNDY METHOD OF MAKING FINNED TUBES Original Filed Dec. 30. 1927 I INHVENTOR.

"7 W 9 BY f ATTORNEY.

Patented Nov. 3, 1931 HABBY 'W. BUNDY, 035' DETROIT, MICHIGAN, ASSIGNOR, BY MESNE'ASSIGNFIENTS, 'IO

nunnr'runme comrm, or

DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN fmn'rnon or MAKING FINNEID means I Application filed December 80, 1927, Serial No. 243,511. RenewedApril 8, 1931.

This invention relates to a finned tube and method of making same.

Finned tube has many uses particularly in connection with. apparatus which requires transference of heat and as examples'ofsuch use, the automobile radiator and condensing units of mechanical refrigerators may be cited. In making up an apparatus employing fin tube, however, difliculties have been 0 encountered in bending thetube into proper shape, because tube provided with .a helical fin which is soldered or otherwise sealed onto the tube is rendered-quite stiff and rigid by reason of the fin. v

The principal object of the present invention is the provision of a finned tube capable of being comparatively easily bent or shaped,

and with this in mind, the invention provides a tube consisting of a preformed tubular body with the helical fin applied to the body without the use of any sealing metal. This fin' is applied-to the tube with a considerable degree of tightness and in such a manner that it will not become loose or move longitudinally or lengthwise of the tube. A tube thus constructed may be nicely bent or shaped into relatively sharp curses for making up condenser units, or the like, out of relatively long lengths of tube, whereas a solder or.

otherwise sealed. fin tube could not be bent Fig. 5 illustrates the tubeof Fig.4 it is into curves sufiiciently sharpfor the purpose. In the accompanyingdrawings: Fig. 1 is a side view with parts in section showing how the'fin may be applied to a preformed tube. I

- ig. 2 is a side view partly in section show- I ing a completed tube.

Fig. 3 is a view similar to Fig. 2 but indieating how the tube'may be bent or curved.

I Fig. 4 is a view partly in section and partly in side elevation showing a modified-form of tube.

curved.

Fig; 6 isa view taken on line 6-6 of Fig. 1, showing the preformedgtube.

Fig. 7 is an enlarged view. insecticn illustheapplication of the helical to trating the manner in which the tube is grooved.

construction but which is preferably a tube made from strip stock which is rolled transversely into tube form; it may be ofsingle ply or double ply wall construction, and the type of longitudinal seam may vary ;'all these details of construction of the preformed tube may be changed to meet various requirements.

The -fin is formed by fin stock which is preferably angular in cross section, the leg in a winding head 4 which includes pressure As shown in Fig. 1, the tube 1 is received rolls 5 and 6 having oppositely disposed engaging the fin forming leg 3. The winding heador fin applying mechanism is fully described and claimed in my patent application Serial No. 243,512, filed December 30, 1927, and for the purposes of the present invention it is not necessary to again describe it here.

I Suifice to say, however, that the rolls 5 and .6 aredriven and engage the fin stock soas to feed the same.

Also these rolls engage the fin leg withconsiderable pressure which is suflicient to compress the metal of this leg with a progressively increasing amount of compression from the band 2 to the outer edge of the le '3, thus to give the fin stock a curvature. t will readily be understood that when the leg 2 is given a helical formation around the tube the diameter of the outside edge of the fin forminglegmust be greater than theinner, andthe compression of the metal therein provides for this. The winding head also includes what might be termed a lead die 7 having a slanting or-cam surface 8 which engages with the fin and sets the' pitch of thehelical fin. This also is fully described in the aforementioned application; f In theform of tubes shown in Figs. 1 to 3 inclusive, the pitch of the helical fin is such that the adjacent convolutions of the leg 2 abut against each other. This construction with the convolutions' thus abutting would surfaces which engage between them,

vary in pitch in accordance with the variance of the width of the leg 2. Y

The curvature given to the fin is such that the normal inside diameter of the helical fin is less than the outside diameter of the tube, thus, the fin tightly grips the tube. In fact, the fin is preferably wound upon the tube with such a degree of tightness as to indent or partially collapse the wall of the tube, as shown at 10. This indentation or partial collapse lies approximately underneath the fin forming leg 3, and takes the form of a helical groove in the body of the tube. Thus, the fin stock as it'tightly grips the tube, seats in this helical curve in the tube body. The fin stock can not come loose from the tube, nor can it move lengthwise of the tube because of'being seated in this helical groove. There is, however, sufiicient give m: slight play which can be effected to permit bending or curving of the tube as indicated in Fig. 3, whereas, if the fin or leg 2 thereof was sealed to the tube by solder or other metal the tube would have a greater stifiness and rigidity and could not be bent into relatively sharp curves.

The invention is also embodied in the modilied form of tube shown in Figs. 4 and 5. In

this form of tube the fin stock is applied so that adjacent convolutions of the leg 2a overlap each other. In this form, however, the same principles of fin application are adhered to and the tube is grooved or partially collapsedas at 1011. It will be noted that the leg 21 of oneconvolution of the fin stock imderlies the fin forming leg 3a of the next adjacent, and that the curving or partial collapsing is also effected in the leg 2a, as shown at 11.

7 Another feature of this tube may be mentioned, and this'feature resides in thefact that the tube is strengthened by the helical band fo med by the leg 2a of the fin stock. While this manner of'reinforcin the tube is shown in a previously filed application of mine, it has a particular associationwith the present invention in that a reinforced tube is provided which at the same time is. not rendered unduly stifi or rigid by such reinforcement. It is thus possible to utilize preformed tube 1, made up of thin stock which would not have sufiicient strength for the purpose were it not for the helical reinforcing band. Another feature is the fact that the tube thus constructed can be bent in curves which are sharper than the preformed tube alone could be bent without the fin. Inotherwords, a thin walled tube without a fin, when being bent in a sharp curve, would collapse; that is, the wall of the tube on the inside of the curve would bend or break at a sharp angle. It has been found, however, that such a tube with the helical fin thereon is reinforced by thefin and a collapse of this nature is prevented. The reason for this is assigned to the fact that the wall of the tube, on the inside curve, is strengthened and reinforced by the helical fin stock.

Claims:

1. The method of providing a helical fin on a preformed tube, which comprises winding helical fin stockon the tube with suificient initial tightness to partially collapse the body of the tube thus to provide a helical groove in the body of thetubc in which the fin seats.

2. The method of providing a helical fin on a preformed tube which comprises winding fin stock on the tube which is angular in cross section with one leg of the angle forming a helical fin, and the other leg forming a helical band on the tube, effecting a tight winding of the fin stock sufficient to partially collapse the body of the tube to form a helical groove substantially underlying the helical fin in which the fin stock seats to form the only connection between the tube and the fin stock.

3. The method of attaching a helical fin to a preformed tube which comprises, winding cold fin stock of angular formation in cross section on the tube to form a helical fin with the adjacent convolutions in contacting relation and the winding so tight that no other fastening means is needed.

4. A method of providing a fin on a preformed tube which com rises substantially simultaneously winding 11 stock on the tube and effecting a depression or groove in the wall of, the tube by partial collapse of the tube wall underneath the wound fin stock, and seating the fin stock in this groove.

In testimony whereof I afiix my signature.

HARRY W. BUN DY.

IOU 

